: fuel air mixture

12-06-05, 05:37 PM
I keep getting codes saying fuel trim is lean, but no other codes to go along with it saying why. what could this be? (96 deville n*)

12-06-05, 05:46 PM
Hmmm....bad Fuel Pressure Regulator? Bad fuel pump? Clogged fuel filter? Pinched fuel line? Vacuum leak? Clogged injectors?

12-06-05, 06:34 PM
Lean fuel trims are usually caused by a vacuum leak.
You could have low fuel pressure which could be caused by lots of things, but I'd start by testing for a vacuum leak. I am sure someone could suggest a few methods.
I use a can of carb cleaner or brake spray but I also use the scan tool and watch the fuel trim readings as I spray. It's easy to see the numbers change but hard to "feel" the rpm change as you spray unless you hit the leak dead on.